The present invention is related to apparatus for feeding individual packing trays from nested stacks.
The packaging industry frequently makes use of layer dividing trays constructed of molded paper pulp or plastic resin. There are several forms of such trays. Efforts have been made to mechanically feed the individual trays to packing stations where the may be mechanically or manually inserted into a case. Such efforts to this point have been unsuccessful.
One difficulty arises due to the rough texture and molded nature often encountered of the trays themselves. The indentations formed within the nested trays tend to adhere together and form vacuum pockets between one another. Also, the edges of the trays tear easily and the trays themselves will readily bend or tear if mishandled.
Attempts to remove trays vertically downward from a stack by applying vacuum force to the underside of each tray have been made by the applicant. However, some trays do not have adequate marginal flanges to support the stack in a vertical hopper. Others have lower surfaces that are too rough for proper vacuum attachment.
U.S. Pat. No. 3,907,161 to Eberhard Martin discloses an apparatus for denesting stacked packaging trays of a specific form from a vertically nested stack. The apparatus utilizes a vertically movable mandrel and vacuum head arrangement whereby the periphery of the individual trays is reduced, disengaging its edges from retaining projections at the lower end of the hopper. The retracted peripheral edge clears the retaining edges and allows the tray to be withdrawn downwardly from the hopper while the next successive tray with expanded edges engages the hopper projections. The device also includes provisions for de-nesting trays from an inclined hopper. Here, the trays are turned from a "face down" to a "face up" position on a conveyor by a rotatable suction mandrel that is indexed inwardly to grasp and reduce the peripheral circumference of the individual tray, pull it outwardly of the nested stack, and pivot it to a horizontal orientation. At that point, the tray is released and falls into a guide mechanism. A rearward edge of the falling tray strikes against a stationary abutment to flip the opposite side of the tray over onto the working flight of the conveyor.
U.S. Pat. No. 3,606,960 to L. J. Butterworth discloses an egg carton dispensing machine making use of an arcuate hopper for nested egg cartons. A pivoted suction head is provided at one side of the bottom hopper end. The suction head is pivoted to engage the convex surfaces of individual egg-receiving indentations. Suction is applied and successive cartons are removed as the suction head arm is pivoted outwardly. The pivot arms are relatively short so that the suction head can engage the carton at a point directly adjacent the pivot axes for the suction heads. Therefore, the tendency is for the cartons to fall onto a conveyor below the hopper in an upwardly open configuration, ready to receive eggs. The suction head merely allows controlled fall of the individual cartons from the nested stack.
The present device makes use of a support arm and suction heads that are pivoted adjacent one transverse side of the nested stack. The suction heads engage the individual trays adjacent an opposite side of the stack. The tray is pulled from the stack and is gradually pivoted from one side of the stack to the other. This reduces the vacuum drag from the one tray to the next. The trays are inverted from the original nested position as the arms are pivoted through an arc of approximately 90.degree. before the trays are released. The guide mechanism assures that the tray will fall vertically onto a working flight of the conveyor below.